Tuesday, December 11, 2018

Microsoft released its monthly security update today, disclosing a variety of vulnerabilities in several of its products. The latest Patch Tuesday covers 38 vulnerabilities, nine of which are rated “critical” and 29 that are considered “important.” There are no “moderate” or “low” vulnerabilities in this release.

The advisories cover bugs in the Chakra scripting engine, several Microsoft Office products and the Microsoft Internet Explorer web browser.

Critical vulnerabilities

Microsoft disclosed nine critical vulnerabilities this month, which we will highlight below.

CVE-2018-8583, CVE-2018-8617, CVE-2018-8618, CVE-2018-8624 and CVE-2018-8629 are all memory corruption vulnerabilities in the Chakra scripting engine that could allow an attacker to execute code on the victim machine remotely. All of the bugs lie in the way the scripting engine handles objects in memory in the Microsoft Edge web browser. An attacker could exploit these vulnerabilities by tricking a user into visiting a web page using Microsoft Edge, or by tricking them into clicking on specially crafted content on other sites that accept user-created content.

CVE-2018-8540 is a remote code injection vulnerability in the Microsoft .NET framework. An attacker can exploit this flaw by passing a specific input to an application utilizing vulnerable .NET methods. If successful, the attacker could take control of an affected system.

CVE-2018-8626 is a remote code execution vulnerability that exists in Windows DNS servers when they fail to properly handle requests. An attacker could run arbitrary code on an affected system if they exploit the vulnerability by sending malicious requests to a Windows DNS server. Windows servers that are configured as DNS servers are susceptible to this vulnerability.

CVE-2018-8631 is a remote code execution vulnerability in Internet Explorer. The bug lies in the way the web browser accesses objects in memory. An attacker could exploit this bug by tricking a user into visiting a specially crafted, malicious web page in Internet Explorer. If successful, the attacker could execute arbitrary code in the context of the current user.

CVE-2018-8634 is a memory corruption vulnerability in the Microsoft Edge that exists when the web browser improperly handles objects in memory. An attacker who successfully exploits this flaw by tricking a user into visiting a malicious, specially crafted web page could gain the ability to execute arbitrary code on the machine in the context of the current user.

Important vulnerabilities

This release also contains 29 important vulnerabilities, eight of which we will highlight below.

CVE-2018-8597 and CVE-2018-8636 are remote code execution vulnerabilities in Microsoft Excel that exist when the software fails to properly handle objects in memory. An attacker can exploit these bugs by tricking the user into opening a specially crafted Excel file, either via the web or as an email attachment. If successful, the attacker could gain the ability to execute arbitrary code on the system in the context of the current user.

CVE-2018-8587 is a remote code execution vulnerability in Microsoft Outlook that exists when the software fails to properly handle objects in memory. An attacker could exploit this vulnerability by tricking the user into opening a specially crafted email attachment while using the Outlook client. If successful, the attacker could use a specially crafted file to perform actions in the security context of the current user. For example, the file could act on behalf of the logged-on user with the same permissions as the current users.

CVE-2018-8590 is a remote code execution vulnerability in Microsoft Word that exists when the software fails to properly handle objects in memory. An attacker could exploit this vulnerability by tricking the user into opening a malicious, specially crafted Word document, either via email, the web, or another vector.

CVE-2018-8619 is a remote code execution vulnerability that exists when the Internet Explorer VBScript execution policy improperly restricts VBScript in certain scenarios. An attacker could use this vulnerability to run arbitrary code with the permissions of the current user. A user could trigger this vulnerability if they visited a specially crafted web page using Internet Explorer.

CVE-2018-8625 is a remote code execution vulnerability in the VBScript engine. The vulnerability could corrupt memory in such a way that an attacker could execute code in the context of the current user. An attacker could trigger this flaw by tricking the user into visiting a specially crafted website on Internet Explorer. Additionally, they could embed an ActiveX control marked “safe for initialization” in an application or Microsoft Office document that hosts the Internet Explorer rendering engine.

CVE-2018-8628 is a remote code execution vulnerability in Microsoft PowerPoint that lies in the way the software processes objects in memory. An attacker could exploit this bug by tricking the user into opening a specially crafted, malicious PowerPoint file, which would eventually grant them the ability to execute code remotely in the context of the current user. The Preview Pane is not an attack vector this vulnerability — the user must open the file in PowerPoint.

CVE-2018-8643 is a remote code execution vulnerability that exists in the scripting engine handles objects in memory in Internet Explorer. An attacker could exploit this bug by tricking a user into visiting a specially crafted web page on Internet Explorer. Additionally, they could embed an ActiveX control marked “safe for initialization” in an application or Microsoft Office document that hosts the Internet Explorer rendering engine. If successful, the attacker could then corrupt memory in such a way that they could execute arbitrary code in the context of the current users.

Coverage

In response to these vulnerability disclosures, Talos is releasing the following SNORTⓇ rules that detect attempts to exploit them. Please note that additional rules may be released at a future date and current rules are subject to change pending additional information. Firepower customers should use the latest update to their ruleset by updating their SRU. Open Source Snort Subscriber Rule Set customers can stay up-to-date by downloading the latest rule pack available for purchase on Snort.org.